1. Field of the Invention
The present invention relates to a composition of a dielectric for a plasma display panel, and more particularly, to a composition of a dielectric applied to a dielectric thick film coated at the upper surface of a transparent electrode of a front substrate (a substrate on which characters or picture is displayed) of a plasma display panel.
2. Description of the Background Art
Recently, a research and development for flat panel display apparatuses such as a liquid crystal display (LCD), a field emission display(FED) or a plasma display panel(PDP) is actively being conducted. Especially, the PDP is the most remarkable owing to its advantages in that it is easily produced due to its simple structure, a memory function, and a wide view angle more than 160xc2x0 is attained, and a large screen more than 40 inches can be implemented.
FIG. 1 is a schematic view showing a structure of a plasma display panel in accordance with a conventional art.
As shown in the drawing, the conventional plasma display panel includes a rear substrate 10 on which address electrodes 11 are mounted, a rear dielectric thick film 12 coated with a predetermined thickness on the upper portion of the rear substrate 10 for charging a wall charge, barrier ribs 13 formed on the upper portion of the rear dielectric thick film 12, separating discharge cells 30; a fluorescent material 14 excited by a light generated in plasma discharging, a front substrate 20, a counterpart of the rear substrate, for displaying a picture or characters, a transparent electrode 21 formed at the lower surface of the front substrate 20, a front dielectric thick film 22 coated with a predetermined thickness, for charging the wall charge; and a protective film 23 coated at the upper portion of the front dielectric thick film 22, for protecting the front dielectric thick film 22 from sputtering caused by discharging.
When a predetermined driving voltage (i.e., 200 V) is applied to the address electrode 11 and to the transparent electrode 21, a plasma discharge is generated due to the electrons discharged from the address electrode 11 in the discharge cells.
In detail, as the electrons discharged from the electrode collides with atom of a mixture of gases of He and Xe or of a mixture of gases of Ne and Xe sealed in the discharge cells, the atoms of the mixture of gases are ionized, so that the second electrons are discharged. At this time, the second electrons collide repeatedly with the atoms of the mixture of gases, sequentially ionizing the atoms of the mixture of gases. That is, it goes to avalanche process in which the electrons and ions are increased double. The light generated in the avalanche process emits fluorescent material of a red color (referred to as xe2x80x98Rxe2x80x99 hereinafter), a green color (referred to as xe2x80x98Gxe2x80x99 hereinafter) and a blue color (referred to as xe2x80x98Bxe2x80x99 hereinafter). The light of R, G and B emitted from the fluorescent material proceeds by way of the protective film, the front dielectric thick film and the transparent electrode to the front substrate 20, thereby displaying characters or graphics.
In this respect, the front dielectric thick film 22 coated on the front substrate 20 needs to transmit the light generated from the fluorescent material. Thus, it requires a property of a high transmissivity. In addition, in order to lower the discharge voltage, it requires a property of a high dielectric constant. Besides, the front dielectric thick film 22 necessarily has characteristics of a low thermal expensive coefficient, thermal stability, a low sintering temperature and a fine organization, and an excellent matching between the electrode material and the protective film.
In order to meet the requirement, the principle ingredient of the composition for fabricating the front dielectric thick film of the conventional art is a PbOxe2x80x94B2O3xe2x80x94SiO2 glass, and its specific composition ratio is as follows. That is, on the assumption that the weight of the PbOxe2x80x94B2O3xe2x80x94SiO2 glass is 100 wt %, its composition ratios are 50-85 wt % of PbO, 10-20 wt % of SiO2, 10-20 wt % of B2O3, 0-10 wt % of K2O, 0-10 wt % of Na2O.
A method for fabricating a dielectric thick film comprised of the composition of a dielectric having the above composition ratio will now be described.
First, the PbOxe2x80x94B2O3xe2x80x94SiO2 glass mixed with the above-described composition ratio is made to a fine powder below 10 xcexcm. Subsequently, the fine powder is mixed with a organic solvent to make a paste or a slurry, which is then coated on the glass substrate (front substrate of the PDP) with a thickness of 20xcx9c30 xcexcm. Finally, after the paste or the slurry coated on the glass substrate is dried for 15xcx9c20 minutes at the temperature of 300xcx9c350xc2x0 C., it is sintered at the temperature of 580xcx9c590xc2x0 C., thereby obtaining a transparent dielectric thick film. Such dielectric thick film having the above composition ratio in accordance with the conventional art has the following characteristics.
Namely, the light transmissivity (%), the most critical characteristic of the dielectric thick film for the front substrate, is approximately 75-85% on the basis of a 400xcx9c800 nm visible ray, its dielectric constant is 12xcx9c14, its thermal expensive coefficient is 65xcx9c90xc3x9710xe2x88x927/xc2x0 C., and its withstand voltage is more than 1.5V
In detail, since the dielectric constant is relatively low, the plasma discharge voltage is increased. And, since radio of the PbO is so high that the plasma display device weighs heavy. Also, due to the high content of PbO, its light transmissivity is low, and thus, the light emitting efficiency of the plasma display panel is low. Moreover, its fabricating process causes a problem of an environmental pollution. In addition, due to the high sintering temperature, the glass substrate (the front substrate of the plasma display panel) is easily deformed and damaged during a certain process.
Generally, the material for the dielectric thick film to be formed on the upper surface of the rear substrate should have characteristics of a low dielectric constant, a high reflectivity, a low sintering temperature, while the material for the dielectric thick film to be formed on the front substrate should have characteristics of a high dielectric constant, a high light transmissivity and a low sintering temperature.
Accordingly, it is required to develop a material that would satisfy the characteristics of the dielectric thick film for the front substrate of the plasma display panel.
Therefore, an object of the present invention is to provide a composition of a dielectric for a plasma display panel in user for fabricating a dielectric thick film for a front substrate having a low sintering temperature, a low thermal expensive coefficient, a high dielectric constant and a high withstand voltage.
To achieve these and other advantages and in accordance with the purposed of the present invention, as embodied and broadly described herein, there is provided a composition of a dielectric for a plasma display panel using a P2O5xe2x80x94ZnOxe2x80x94PbO glass.
In order to achieve the above objects, there is also provided a composition of a dielectric for a plasma display panel using the P2O5xe2x80x94ZnOxe2x80x94PbO glass that has the composition radios of 30xcx9c60 wt % of P2O5, 5xcx9c40 wt % of PbO, 0xcx9c5 wt % of MgO, 0xcx9c5 wt % of CaO, 0xcx9c10 wt % of La2O3, 0xcx9c5 wt % of SrO, 1xcx9c5 wt % of Al2O30xcx9c2 wt % of Sb2O3, 0xcx9c2 wt % of As2O3, 5xcx9c25 wt % of BaO, and 0xcx9c5 wt % of TeO2.
In order to achieve the above objects, there is also provided a composition of a dielectric for a plasma display panel using the P2O5xe2x80x94ZnO-PbO glass mixed with an oxide filler.
In order to achieve the above objects, there is also provided a composition of a dielectric for a plasma display panel using the P2O5xe2x80x94ZnOxe2x80x94PbO glass mixed with the oxide filler, of which the oxide filler refers to at least one of PbTiO3, Bi2O3, BaTiO3 CaTiO3, CaSnO3, PbZrO3 and CaSiTiO.